In one known electrical switching device in the form of a low-voltage circuit breaker, the switching chamber enclosure includes a front and a rearward enclosure part. Each have a circumferentially closed surface and absorb mechanical forces that occur during operation of the moveable switching contact. These forces act essentially at right angles to the contact surfaces of the switching contact system. In the normal way for low-voltage circuit breakers, the two enclosure parts rest against one another along a separating joint. The joint runs parallel to the axis of the switching shaft. When the switching device is in the in-use position, it runs vertically between the enclosure front wall and the enclosure rear wall.
Since one contact is associated with the front enclosure part and the other contact is associated with the rearward enclosure part, this arrangement requires that the enclosure parts be aligned correctly with one another, such that they match. This arrangement of the contacts also means that the forces which are associated with the switching processes and which run at right angles to the contact surfaces of the switching contacts act on the enclosure parts at right angles to the separating joint. Generally, this means that the enclosure parts must be held together using tie rods (U.S. Pat. No. 4,764,650). Furthermore, a configuration of the switching chamber enclosure such as this makes it necessary to remove the rear wall, in order to gain access to the appropriate assemblies, for the purpose of maintenance or repair of the switching contact systems. Once the appropriate work has been carried out, the front wall and the rear wall must be joined together once again.
With a conventional construction, an enclosure part which is stressed in such a way is subject to mutual alignment via the tie rods via a constriction in the through-holes. When tie rods such as these are used, this results in considerable difficulties in the production of the enclosure parts and of the stamping tools which are required for their production.
Firstly, the manufacturing processes are subject to tight tolerances. Secondly, it is possible for problems to occur during assembly as a result of screws becoming jammed, since the through-holes are formed by relatively long and thus unstable pins in the stamping tool. These pins can be elastically deformed by the stamping force and by the displacement of the substance being molded, as a result of which the through-holes for the tie rods may be misaligned.
In another known low-voltage circuit breaker, an additional element is used to reinforce the connection between the enclosure parts. This element, which is in the form of a dovetail, is arranged between the enclosure parts and extends along the side walls of the enclosure parts within a channel, which is formed by the two enclosure parts, in order to hold the element. This element is used to increase the strength of the connection between the enclosure parts with regard to force transmission, but contributes to mutual alignment of the enclosure parts at most in one plane, namely the horizontal. It also uses a relatively large amount of material and results in additional assembly effort (U.S. Pat. No. 4,899,253).